Long chain dicarboxylic acids are basic monomer raw materials of a series of synthetic materials. Long chain dicarboxylic acids and derivative monomers thereof can be used for producing nylon, polycarbonate, powder coatings, perfumes, hot melt adhesives and special lubricants and the like, and are important raw materials for such products as synthetic perfumes, engineering plastics, cold resistant plasticizers, high grade lubricants and polyamide hot melt adhesives.
During the preparation of a long chain dicarboxylic acid, a long chain dicarboxylate is firstly formed in a reaction solution generally, and the reaction solution containing the long chain dicarboxylate needs to be subjected to a series of treatments, so as to obtain a long chain dicarboxylic acid product.
During a biological fermentation process for producing a long chain dicarboxylic acid, a fermentation broth after the fermentation is ended contains a long chain dicarboxylate, and further contains microbial cells and other impurities, such as residual alkanes or fatty acids. The fermentation broth needs to be treated, so as to obtain the long chain dicarboxylic acid.
Presently, a process for obtaining a long chain dicarboxylic acid from a fermentation broth includes performing pretreatments such as microbial cells removal, decolorization, acidification, filtration and the like firstly to obtain a primary product, and then performing treatments such as recrystallization, decolorization, washing and the like. The steps of this process are too long, and the production costs are high.
Chinese Patent Application No. 200410018255.7 teaches a process for producing a normal long chain dicarboxylic acid, wherein a fermentation broth is subjected to a series of treatments of microbial cells removal by a ceramic membrane, decolorization by active carbon, acidification by an inorganic acid, plate-and-frame filtration and the like, so as to obtain a dicarboxylic acid product. The treatment process has the following disadvantages: 1) the process route is complex, the operation cycle is long, more equipment is required, and the production efficiency is low; 2) the product yield is low and generally is 93% to 95% only; 3) the product quality is poor, the salt content of the resulting dicarboxylic acid product is high, and the color is dark; 4) a large amount of active carbon is needed to be consumed, and the amount of the active carbon used is up to 5% to 10% based on the amount of the product, which causes waste of resources and environmental pollution because the active carbon after the decolorization cannot be recycled. The dicarboxylic acid product obtained through this process needs to be subjected to further refining treatments, so as to meet the requirements of most customers for the quality of the long chain dicarboxylic acid.
A novel process for directly treating a reaction solution to obtain a long chain dicarboxylic acid product at a high yield has been always desired.